<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
       //undefined
       //var X;
       //alert(X)
       //字符
       var str1="hello,word";
       var str2="hello,word";
       console.log(str1)
       console.log(str2)
       //var str3="hello word"
       var str4='小明说："小红你好漂亮"'
       console.log(str4);
       var str="java";
       //js中先运算等号右边的语句
       str=str+"script";//字符串中+号是连接的意思 javascript
       console.log(str);
    </script>
</body>
</html>